Image projector and image projecting method

ABSTRACT

In an image projection on a screen, an image projection apparatus improves the safety of entry into a projection region by the human body and does not bring about the increase of complexity of the configuration thereof owing to the improvement of the safety. A monitoring area is regulated on the outside of the projection area ( 3 ) of the screen ( 2 ). A detection wave such as infrared rays is emitted from a detection wave source ( 1   c ) of the image projection apparatus ( 1 ). A reflection wave from the monitoring area is detected by reflection wave detection means ( 1   d ) such as a CCD sensor. Whether the human body or an obstacle enters the monitoring space, which is surrounded by a detection wave ( 4 ) between the main body unit of the image projection apparatus ( 1 ) and the screen ( 2 ), or not is detected. Once the entry is detected, the intensity of the radiation light traveling toward the projection area ( 3 ) is reduced or cut off according to the situation or the degree of the entry.

TECHNICAL FIELD

The present invention relates to a technique for taking a sufficientsafety measure in an image projection apparatus and an image projectionmethod which are constituted by using a high intensity light source.

BACKGROUND ART

As an image display apparatus capable of large screen display, aprojection type projector apparatus is known. A viewer can view aprojected image by projecting light from a light source onto a screen.

As a light source of a projector apparatus, a high luminance projectiontube has been used until now. However, with the object of theimprovement of brightness, color reproducibility and the like, theobject of the easiness of modulation by an image signal, and the otherobjects, a projection system using the laser light sources of red (R),green (G) and blue (B) has been proposed.

In the mean time, when a laser light is used, the securement of thesafety thereof is an important task. For example, it is needed to takean enough measure against the case where a viewer carelessly enters theprojection area of the laser light. That is, a danger in the case wherea laser light directly entered the eye is pointed out. As the safetymeasure thereof, various apparatus having the function of detectingentry into the projection area of the laser light by a person or thelike to cut off the projection of the laser light has been proposed (forexample, see Japanese Unexamined Patent Publication No. Hei 4-111585,Published Japanese Translation of PCT Application No. Hei 11-501419,Japanese Unexamined Patent Publication No. 2001-249399).

Now, the conventional apparatus have the problems caused by taking sucha safety measure. The problems are, for example, that the configurationof an apparatus becomes complicated; that such a measure interferes withmaking the size of an apparatus larger; and the like.

That is, a safety mechanism for the safety of the human body isindispensable for an apparatus attaching importance to the safety.However, when the attachment of the safety mechanism brings aboutdisadvantages such as the growth of the complexity of a projectionoptical system and the like, a remarkable rise of an apparatus cost, andthe like, it is apprehended that the disadvantages cause a hindrance ofdiffusion and the like. Moreover, no delay of the operation of thesafety mechanism is allowed, and the rapidity of entry detection isrequired.

Accordingly, the present invention aims to improve the safety of animage projection apparatus including the function of projecting an imageon a screen to display the image thereon in the case where the humanbody or the like enters the projection region of a radiation light, andnot to bring about the increase of the complexity of the configurationof the apparatus, and the like owing to the improvement of the safety.

DISCLOSURE OF THE INVENTION

For solving the problem, an image projection apparatus according to thepresent invention is constituted to include: a detection wave sourceprovided on an opposed surface of an apparatus main body unit to ascreen or on the screen; and reflection wave detection means fordetecting a reflection wave reflected on a monitoring area located on anoutside of a projection area on the screen at a distance after adetection wave has been emitted from the detection wave source towardthe monitoring area, whereby entry into a monitoring space surrounded bythe detection wave is detected on a basis of a result of a comparison ofa detected level by the reflection wave detection means with aprescribed threshold value or a reference region.

Moreover, an image projection method according to the present inventionregulates a monitoring area located on an outside of a projection areaon a screen apart from the projection area, the screen located at adistance from an image projection apparatus, and emits a detection wavefrom a detection wave source provided on a front surface of the imageprojection apparatus toward the monitoring area, and further detectsentry into a monitoring space surrounded by the detection wave bydetecting a reflection wave from the monitoring area, and thereby cutoffs light radiated toward the projection area or reduces intensity ofthe light according to an entry state.

Consequently, according to these inventions, a detection wave sourceopposed to a screen is provided, and a reflection wave emitted from thedetection wave source and reflected from a monitoring area is detected.Accordingly, entry into a monitoring space can be detected with a simpleconfiguration. Then, when the entry into the monitoring space isdetected, it is possible to prevent the human body from being exposed todanger by cutting off a radiation light to a projection area or byreducing light intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a basic configuration example of animage projection apparatus according to the present invention;

FIG. 2 is an explanatory view exemplifying each of projection areas andmonitoring areas on a screen;

FIG. 3 is a view for illustrating an intensity distribution of adetection wave radiated on the periphery of the screen;

FIG. 4 is a flowchart representation explanating a safety measure in theimage projection apparatus;

FIG. 5 is a view for explanating a configuration example of an imageprojection apparatus, and showing a view of an arrangement example of aprojector apparatus and a screen unit;

FIG. 6 is a front view of the projector apparatus shown in FIG. 5;

FIGS. 7A, 7B, 7C and 7D are views illustrating an example of infraredray radiation means;

FIGS. 8A and 8B are views showing a radiation example of the infraredray radiation means;

FIG. 9 is a view showing a configuration example of a projection system;

FIG. 10 is a flowchart representation showing a process example of anentry detection and danger prevention control unit;

FIG. 11 is a graphical representation showing an example of timeprogress of a laser light power level;

FIG. 12 is a graphical representation exemplifying a relation between aninfrared ray intensity and a distance;

FIGS. 13A, 13B and 13C are views for illustrating a setting method ofprojection regions of detection waves and monitoring areas;

FIG. 14 is a view showing another example of the configuration of theprojection system;

FIGS. 15A and 15B are views showing a positional relation between theprojector apparatus and the screen shown in FIG. 14;

FIG. 16 is a flowchart representation exemplifying alarm operation ofthe projector apparatus of FIG. 14;

FIG. 17 is an explanatory view exemplifying the detection area of asecond detection means with regard to the detection of entry into secondmonitoring space;

FIG. 18 is an explanatory view exemplifying other detection areas of thesecond detection means;

FIG. 19 is an explanatory view exemplifying a detection area in case ofusing ultrasonic sensors as a first detection means with regard to thedetection of entry into first monitoring space; and

FIG. 20 is an explanatory view showing another example of firstdetection means.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention aims to secure safety by immediately cutting offlight or reducing light intensity when an obstacle enters the projectionarea of a radiation light (such as a laser light or the like) in animage projection apparatus.

FIG. 1 schematically shows a basic configuration example of an imageprojection apparatus according to the present invention, and shows anexample of an apparatus using a laser light source (a laser projectorapparatus and the like).

An image projection apparatus 1 includes a light source 1 a forperforming image display by projection to a projection area 3 on ascreen 2 located at a fixed distance from an apparatus main body unit,and a projection unit 1 b including a projection lens. For example, aconfiguration which is provided with laser light sources (the laserlight source of each color of R, G and B) and an optical modulator(modulation means) and includes the function of projecting an image onthe screen 2 by the use of the laser lights is known. Incidentally, theoptical modulator is provided with a modulator, which modulates thelaser light of each color of R, G and B according to an image signal andan optical system. The laser lights are modulated according to the imagesignal, and scanning (a sweep) is performed by means of, for example, agalvanometer mirror or the like constituting optical sweep means.Moreover, the optical modulator is provided with a projection opticalsystem including an objective lens for projecting the laser light ofeach color on the screen 2. The laser light of each color swept by theoptical sweep means is irradiated on the screen 2 through the projectionoptical system. Incidentally, the present invention can be applied notonly to the projector apparatus in the form of modulating illuminationlights by means of an image signal while projecting the modulated lightson the screen, however also to projector apparatuses having variousconfiguration forms.

Incidentally, as the light source la, the configuration using anelectric discharge lamp, an arc tube or the like, which have high lightintensity or high luminance can be cited, however, in particular, theconfiguration form using laser light sources has superiorcharacteristics in brightness or color reproducibility as compare to theconfiguration using the projection tube or the like, and by theconfiguration form using the laser light sources, the modulation of animage signal is easy. However, as described above, in the case where thelaser light sources are used, it is needed to take a safety measureagainst the entry into the radiation light passing area, which is fromthe projection unit 1 b to the projection area 3 on the screen, by thehuman body or the like (for example, the cut off of the laser lights,the reducing of the light intensity, or the like).

In FIG. 1, a rectangular frame “LA” indicated by a full line on thescreen 2 indicates the outline frame of the projection area 3 of thelaser lights. In the area, an image is projected to be displayed.

The image projection apparatus 1 is equipped with a safety mechanism forthe prevention of danger on the human body (such as the mechanism forpreventing the direct entering of the laser lights to the eye, or thelike) even when, for example, a viewer carelessly enters the irradiatedregion of the laser lights toward the projection area 3. In entrydetection to a setting area (monitoring space), the image projectionapparatus 1 utilizes a detection wave to detect the reflection wave ofthe detection wave. Then, when entry into the area by a person or thelike is detected, the image projection apparatus 1 cut offs theradiation lights to the projection area 3, or reduces the intensity ofthe radiation lights sufficiently (the image projection apparatus 1prevents the influence of the light to the eyes of the person).

Entry detection means using the detection wave includes a detection wavesource 1 c and reflection wave detection means 1 d.

The detection wave source 1 c is provided on the front surface of theapparatus main body unit opposed to the screen 2 or on the screen. Asthe detection wave source 1 c, for example, a safe light source such asa light emitting diode (LED) can be used as a light emission source ofinfrared light or infrared rays (even when the infrared light enters theeyes of a viewer, no safety problems are caused).

A detection wave 4 emitted by the detection wave source 1 c (see two-dotchain lines in FIG. 1) is irradiated toward the screen 2. In FIG. 1, arectangular frame IR shown by a broken line on the screen 2 indicatesthe projection area of the detection wave. In the present embodiment,the projection area is a quadrilateral area which is located on theoutside of the projection area 3 of the laser lights and is formed to bea size larger than the area. Incidentally, the reason why the projectionarea (the rectangular frame IR) of the detection wave is set to belarger than the projection area 3 of the laser lights in size (an angleof view) is that it is necessary to detect the entry into the projectionarea 3 by a viewer or the like before the entry.

The reflection wave detection means 1 d is provided for detectingreflection waves of the detection wave from the screen. That is, afterthe detection wave has been emitted from the detection wave source 1 ctoward a prescribed area (see a monitoring area 6 in FIG. 2) locatedseparately on the outside of the projection area 3, the reflection wavedetection means 1 d detects the reflection waves reflected in the area.When, for example, infrared light or infrared rays are used as thedetection wave, an image sensor (such as a charge coupled device (CCD)type image sensor, a complementary metal-oxide semiconductor (CMOS) typeimage sensor, or the like) can be cited as the reflection wave sensor ofthe detection wave.

Incidentally, the detection wave source 1 c and the reflection wavedetection means 1 d are arranged around the projection unit 1 b providedon the surface opposed to the screen 2 (the front surface of theapparatus main body unit). As shown in the present embodiment, in caseof the configuration in which the reflection wave detection means 1 d islocated in the neighborhood of the projection unit 1 b and the detectionwave source 1 c is arranged so as to surround them, the configuration isadvantageous for the miniaturization and the compactification of theapparatus. Moreover, by providing the reflection wave detection means 1d at a position near the projection unit 1 b, the occurrence probabilityof erroneous detection and the like can be reduced (for example, whenthe reflection wave detection means 1 d is too distant from theprojection unit 1 b, detection unrelated to the projection is performed.If entry detection responds to the unrelated detection, the possibilitythat the safety mechanism unnecessarily operates is produced) . Inaddition, by the use of the method of modulating the detection wave, andthe like, it is possible to heighten the precision of detection, or toprevent erroneous detection.

FIG. 2 exemplifies the relation among the projection area 3 of the laserlights, a projection area 5 (shown by a region indicated by brokenlines) of the detection wave and the monitoring area 6 on the screen 2.

The monitoring area 6 is set at a position almost corresponding to theprojection area 5, however the width of the monitoring area 6 is set tobe narrower than that of the projection area 5. In the presentembodiment, the monitoring area 6 is composed of four areas 6A-6D whichseverally have a prescribed width and correspond to each side of therectangular frame (a quadrilateral) severally. However, the monitoringarea 6 is not limited to such a shape. It is possible to implement thepresent invention in various forms using at least one or more sides ofmonitoring areas.

Among each of the areas 6A-6D shown in FIG. 2, the area 6A constitutesthe left side part of the quadrilateral; the area 6B constitutes theupper side part of the quadrilateral; the area 6C constitutes the rightside part of the quadrilateral; and the area 6D constitutes the lowerside part of the quadrilateral. Then, with regard to each configurationarea, monitoring is performed correspondingly to each configuration areaon the basis of acquisition data pertaining to a region (a detectionregion) detected by the reflection wave detection means 1 d. Forexample, in the case where a reflection wave sensor, an image sensor orthe like of infrared light or infrared rays is used, entry monitoring isperformed by a process using pixel data constituting the detected imageof each of the configuration areas.

Incidentally, the distance from the external shape frame LA of theprojection area 3 to the monitoring area 6 (see a letter “W” in FIG. 3)is determined on the basis of the relation between an entry speedestimated from the action of the human body or the like and the timerequired from the detection of the entry by the human body or anobstacle to the cut off of the laser lights or the darkening of thelaser lights (namely, when the distance is too short, the danger inwhich the laser light cutting off or the laser light darkening after theentry detection becomes too late is produced. Consequently, it isnecessary to perform the setting of the distance (the interval)suitably).

With regard to the monitoring area 6, for example, the following formscan be cited:

-   -   (a) the form of setting the monitoring area 6 in a region of the        screen where reflectance is high, and    -   (b) the form of providing a reflection member (a retroreflection        sheet or the like) in a region where the reflectance of the        periphery of the screen is low.

In the form (a), image projection is performed in the state in which theprojection area 3 is positioned in the region of the screen 2 where thereflectance is high. In consideration of the fact that the projectionarea 3 is normally set to have a region smaller than the maximum size(the size of a white back ground part) of the screen 2 slightly, theposition of each of the areas 6A-6D is set on the outer periphery of theprojection area 3. That is, in the form (a), the region having highreflectance in the screen 2 can be utilized as it is. On the other hand,the existence of the monitoring area 6 influences the image size of theprojection area 3, and the display region becomes slightly narrower.

Accordingly, in the form (b), a retroreflection sheet or the like ispasted on the periphery of the screen (black back ground part or thelike), and the part is utilized as the monitoring area. Accordingly, itbecomes possible to perform image display on the full screen.

The monitoring area 6 is set to be larger than the projection area 3 insize and position on the basis of a measured value of the distance fromthe image projection apparatus 1 to the screen 2 and the F value of theprojection lens. At this time, the radiation lights having high lightintensity is not outrightly applied to the projection area 3, howeverthe radiation lights having the brightness which is sufficiently safefor the eye are first projected on the projection area 3. Then, it ispreferable to perform the setting of the size and the position of themonitoring area 6 by observing the angles of view of the radiationlights.

FIG. 3 shows a schematic intensity distribution of the detection wave.With regard to a curved line 7 in the graph indicating the intensitydistribution, the intensity of the detection wave is indicated in thedirection designated by an arrow L, and positions on the screen 2 areindicated in the direction perpendicular to the direction designated bythe arrow L.

The detection wave is radiated toward positions distant from the outlineof the projection area 3 to the outside thereof by the intervaldesignated by the letter “W”. The detection wave has a distribution inwhich the detection wave shows an almost constant intensity being aprescribed level or more in a region slightly wider than the width ofthe monitoring area 6 (the widths of the areas 6A-6D) and the intensitygradually decreases as the position moves from the region to the insideor the outside of the screen 2. That is, when the width of themonitoring area 6 is too large in comparison with the width of theprojection area 5, the foot parts of the detection wave, which indicateslow intensities, are included in the monitoring area 6. Consequently,the following problems are produced. That is, the intensity becomesunstable, and a signal to noise (S/N) ratio necessary for detectioncannot be acquired. Accordingly, it is preferable to set the width ofthe monitoring area 6 to be within the projection area 5 of thedetection wave when the monitoring area 6 is viewed from the directionopposed to the screen 2, and to set the width to be within the region(the flat area) in which the intensity of the detection wave is almost aconstant level equal to a prescribed level or more.

Next, a monitoring process will be described.

A principle in the case where each of the areas 6A-6D of the monitoringarea 6 is monitored by the reflection wave detection means 1 d toperform a judgment process related to entry detection is as follows.

Each configuration area of the monitoring area is monitored as, forexample, a detected image by the reflection wave detection means 1 d. Asan example, it is supposed that the size of a certain monitoring area 6Bcorresponds to the image size of “2 pixels in width×600 pixels inlength=1200 pixel in sum” of the corresponding detected image, and thatthe intensity of a reflection wave is shown by means of a prescribedgradation expression with regard to each pixel data. That is, thedetection wave is irradiated in the projection area 5 on the screen 2,and is reflected by the screen. The intensity of the reflection wave isrecognized as the data of each pixel constituting the detected image inthe monitoring area. For example, when the intensity of a reflectionwave from the screen 2 is detected at a precision of 256 gradations, thejudgment of entry detection can be performed by setting a referenceregion of the intensity of the reflection wave based on the pixel datapreviously to examine whether the actual intensity of the reflectionwave is within the reference region or not. When the reference region isregulated to be, for example, the region of 70-120, and when the actualintensity of a reflection wave is smaller than the reference region(0-69), or when the actual intensity of the reflection wave exceeds thereference region (121-255), it is recognized that the detection wave isinterrupt at the pixel indicating the data, or that the detection waveis too bright.

In the case where a reducing of the intensity or a rise of the intensityis perceived by the performance of a judgment of the intensity of thereflection wave being unpermitted based on a comparison result of theintensity of a predetermined number (for example, 6) of pixels or morein the 1200 pixels of the monitoring area with the intensity of thereference region, then it is judged that entry by the human body or anobstacle is made. Incidentally, a change of the detected value of theintensity of the reflection wave based on each pixel data is caused byan interruption of the detection wave by the human body or an obstacle,or by direct reflection of the detection wave by the human body or theobstacle. It is possible to compare a level detected by the reflectionwave detection means 1 d with a prescribed threshold value or thereference region, and to detect entry into the monitoring spacesurrounded by the detection wave on the basis of the comparison result.Incidentally, the “detection” includes the detection of the size or themoving direction of the human body or an object in addition to, needlessto say, their existence itself.

As described above, it is effective not to perform the detection of thewhole detected image, however to perform the detection of a part of thedetected image corresponding to the monitoring area by level comparison.A complicated image process taking a lot of time is unnecessary.

When entry by a person or the like is detected through such a monitoringsystem, the safety mechanism works. That is, the reflection wavedetection means 1 d detects a reflection wave from the screen 2 inconnection with the monitoring area 6 (6A-6D) . The reflection wavedetection means 1 d measures the intensity of the reflection wave fromthe screen 2 on the basis of each pixel data of the monitoring area 6.Then, for example, detects that the intensity of the detection wavereflected by entry into the human body or an obstacle differs from theintensity of the reflection wave from the screen or a reflection member(such as a retroreflection sheet or the like) in the case where no suchentry is made. Then, when abnormality including a reducing or a rise ofthe intensity is detected in any monitoring area, the radiation lights(such as the laser lights or the like) is cut off or darkened. Withregard to the mechanism, for example, the following configuration formscan be cited:

-   -   a form for interrupting the emission light from the light source        1 a by a cutting off mechanism such as a mechanical shutter or        the like,    -   a form of drive control of optical modulation means, for        example, a form of making the drive of an light modulation        element an off state (a dark state),    -   a form for stopping the feeding of a power to the light source 1        a, or for reducing the supply power, and    -   a combination of the forms described above.

FIG. 4 is a flowchart representation for illustrating an example of asafety measure pertaining to the image projection apparatus 1. Accordingto the present algorithm, an accident can be prevented from occurring inthe case where a person carelessly enters the projection region of thelaser lights by performing the projection of a laser light having thesufficiently safe intensity for the eyes of the person until the safetyof the projection of the laser lights is confirmed.

The process steps are as follows:

-   -   (S1) starting operation by turning on the switch of the        apparatus,    -   (S2) irradiating a laser light having the intensity which is        sufficiently safe to the eye,    -   (S3) confirming the set state of the safety mechanism to advance        to (S4) when re-setting is needed or to advance to (S5) when no        problem exists in the setting,    -   (S4) after performing various adjustments and confirmation        processes, return to (S3),    -   (S5) a user or an administrator of the apparatus confirming the        safety to turn on the switch for making the safety mechanism        operate, and    -   (S6) irradiating a laser light in prescribed brightness. As        described above, when entry by the human body or an obstacle is        detected in this state, the laser light is cut off or the        intensity of the laser light is reduced by darkening to the safe        level similarly to (S2).

Incidentally, the adjustment or the confirmation matters at (S4) are,for example, as follows:

-   -   the automatic adjustment and the confirmation of a projection        distance,    -   the setting of a monitoring area based on the projection        distance and the angle of view,    -   the automatic adjustment of a detection wave output, a radiation        position and the like according to the radiation to the screen        and the distance of a detection wave, and    -   the confirmation of the intensity of the reflection wave from        the screen and the change of setting of the screen in response        to the necessity, and the like.

As the present embodiment, the control is preferably performed in orderthat image projection may be performed with the intensity of anradiation light reduced to a level at which the radiation light is notdangerous to the human body until no detection of the entry into themonitoring space surrounded by the detection wave, especially the entryby the human body, is confirmed, and that the intensity of the radiationlight may be raised to a regulated level after the safety has beensufficiently confirmed. Then, after the image projection apparatus 1confirms that the monitoring space is not entered by the human body oran obstacle, a user (an operator of the apparatus) confirms that theprojection area 3 is not entered by the human body or an obstacle tomake double sure, and then the projection output of the radiation lightis not raised until the user turns on a dedicated switch. Thus, thesafety can be further improved.

Incidentally, although (S2)-(S4) mentioned above can be manually orautomatically operated, automation is preferable from the point of viewof the convenience for a user. Moreover, it is preferable that thepreceding adjustment and the setting state are stored in storage meansin the apparatus together with the conditions at that time (theprojection angle of view, the projection distance and the like), andthat the preceding storage information is verified with the informationacquired from the present situation at the time of the next apparatusstart. For example, the image projection apparatus 1 is constituted asfollows. That is, when a verification result is permitted (namely, whenthe verification result does not differ from the preceding stategreatly), the process advances from (S2) to (S5). However, when thesituation has changed from the verification result greatly, theadjustments and the settings are performed over again from thebeginning.

Next, an example of a projector apparatus having the function of entrydetection and danger prevention will be described by reference to FIGS.5-20. Incidentally, it is possible to apply the example to the form fordetecting the entry into the passage area of projection light (a laserlight) by a person to prevent the entering of the light to the eyes ofthe person, and to the form for decreasing the intensity of the light toan undangerous degree.

FIG. 5 is a perspective view showing a projector apparatus main bodyunit and a screen. The project or apparatus includes an apparatus mainbody unit 1A and image means 100 such as a CCD type image sensor(corresponding to the reflection wave detection means 1 d) which ismounted on the apparatus main body unit 1A.

Then, a screen 40 is arranged in front of the projector apparatus. Animage projection area 42 is regulated on the surface of the screen 40. Arectangular monitoring area 46 is regulated on the peripheral area 44 ofthe image projection area 42. Incidentally, in the present embodiment,the monitoring area 46 is composed of monitoring areas 46A-46Dcorresponding to each side of a quadrilateral severally.

FIG. 6 is a front view of the apparatus main body unit 1A. FIG. 6 showsa projection lens 32, the image means 100 and infrared ray radiationmeans 120 (120A-120D).

The projection lens 32 is located in the center of the front surface ofthe apparatus main body unit 1A. An image is projected from theprojection lens 32 to the projection area 42 on the screen 40 (the focallength of the projection lens 32 can be adjusted).

The infrared ray radiation means 120 is located on the periphery of thefront surface of the apparatus main body unit 1A. In the presentembodiment, the infrared ray radiation means 120 includes four infraredray radiation units 120A-120D for irradiating infrared rays. That is,these infrared ray radiation units irradiate infrared rays having aprescribed wavelength (for example, λ=880 nm) to each of the monitoringareas 46A-46D constituting the monitoring area 46.

FIGS. 7A-7D exemplify one (120A) of the infrared ray radiation units.FIG. 7A is the front view thereof. FIG. 7B is the side view thereofshowing a light-emitting device. FIGS. 7C and 7D are explanatory viewsof infrared ray radiation angles.

Each of the infrared ray radiation units 120A-120D has the sameconfiguration. As shown in FIG. 7A, arrays of a plurality oflight-emitting devices (for example, eleven light-emitting diodes forradiating infrared rays in each array) in the longer direction arearranged in two rows in a direction (the vertical direction in thefigure) perpendicular to the longer direction.

As shown in FIG. 7B, each light-emitting diode is provided with acorrection lens “LNS” on the front surface of the light-emitting diode.Then, in the present embodiment, as shown in FIG. 7C, a divergence angle(a wave angle) based on the optical axis direction of the correctionlens is set to 2° in a vertical plane including the optical axis.Moreover, as shown in FIG. 7D, a divergence angle based on the opticalaxis direction is set to 34° in a horizontal plane. Each of the infraredray radiation units irradiates an infrared ray toward the monitoringarea (for example, 46A) corresponding to each of the infrared rayradiation units.

Incidentally, the number of the light-emitting devices used in each ofthe infrared ray radiation units is not necessarily the same to eachother. For example, the using device numbers of the infrared rayradiation units 120B and 120D located on the short sides of thequadrilateral may be less than those of the infrared ray radiation unit120A and 120C located on the long sides of the quadrilateral.

Moreover, each of the infrared ray radiation units is provide with atilt mechanism for making it possible to adjust a radiation angle towardthe screen 40 manually or automatically. That is, because the projectiondistance from the main body unit 1A to the screen 40 and the positionalrelation of both of them are not always fixed, it is preferable toconstitute the project or apparatus in order to be able to adjust theradiation directions, the radiation regions and the like of the infraredray radiation units 120A-120D, and to be able to adjust the focal lengthof the projection lens 32 and the like. The projector apparatus isfrequently used in various situations. The various situations can becited as follows. For example, the case where the projection distance is3 m, and the projection lens 32 and the projection area 42 of the screen40 are in a horizontal positional relation; the case where theprojection distance is 5 m, and a projection image is irradiated fromthe projection lens 32 to the projection area 42 upward; and the likecan be cited (in addition to the capability of the adjustment of thedirection and the focal length of the projection lens 32, it ispreferable that the tilt (the inclination operation) of the infrared rayradiation units 120A-120D is made possible and the tilt angle of each ofthe infrared ray radiation units is made to be adjusted according to thezooming of the projection lens 32 and the like).

For example, it is possible to adjust the infrared ray radiation units120A-120D manually or automatically as shown by an upward arrow “U” or adownward arrow “D” in FIG. 7C according to the projection distance.

FIGS. 8A and 8B are views for illustrating a radiation direction and aradiation width of the infrared ray radiation units. FIGS. 8A and 8Bexemplify the infrared ray radiation unit 120A, and shows the stateswhen the infrared ray radiation unit 120A is viewed from the sidedirection perpendicular to the vertical plane.

It is possible to perform the adjustment or the setting of thedivergence angle and the infrared ray radiation width in the verticaldirection and in the horizontal direction according to the distancebetween the main body unit 1A and the screen 40. For example, an opticalpath setting for making rays (infrared rays) from the infrared rayradiation unit 120A to be almost parallel rays to irradiate themonitoring area 46A as shown in FIG. 8A, an optical path setting formaking radiation rays from the infrared ray radiation unit 120A approachto cross with each other and advance to be away from each other as shownin FIG. 8B, and the like can be cited.

The intensity distribution of the infrared rays to be radiated to theperipheral area 44 of the screen by each of the infrared ray radiationunits is as illustrated in FIG. 3. That is, the curved line 7 in thegraph of FIG. 3 indicates the intensity of the infrared rays, and themonitoring area 46 is located in a region on the screen 40 correspondingto the region of the peak of the intensity (the flat part) . Forexample, the value of the distance “W” is 10 cm, and the width of eachof the monitoring areas 46A-46D is supposed to be all the same, or it isalso possible to change the widths individually as the occasion demands.

The image means 100 images the screen 40 including the monitoring area46. A filter transmitting only an infrared component at the normaloperation of the projector apparatus is formed on the front surface ofthe image means 100. The image means 100 detects the infrared raysreflected from a region including the monitoring area 46 (incidentally,it is needed to remove the filter at an adjustment step which will bedescribed later).

A signal process of an infrared ray image detected through the imagemeans 100 (a detected image by the infrared rays which have passedthrough the filter) is performed by an entry detection and dangerprevention control unit 110 which will be described later.

FIG. 9 is a block diagram showing a configuration example of theprojection system. The projection system includes an optical modulationunit 10, an optical adjustment unit 20, an optical projection unit 30,the screen 40, a power source system 50, a signal process unit 60, theimage means 100, the entry detection and danger prevention control unit110, the infrared ray radiation means 120 and a feeder apparatus 130.

The feeder apparatus 130 feeds electric power to the infrared rayradiation units 120A-120D. By receiving a command from the entrydetection and danger prevention control unit 110, the feeder apparatus130 can change the electric power to be supplied to each of the infraredray radiation units. Accordingly, it is possible to perform theadjustment and the setting of the output level of the light-emittingdevice group constituting each of the infrared ray radiation units.Incidentally, the entry detection and danger prevention control unit 110constitutes the entry detection means. The entry detection and dangerprevention control unit 110 is composed of, for example, a computer(including a memory, a display device and the like), a dedicated circuitand the like.

The optical modulation unit 10 includes a light source unit 12, anillumination light generation unit 14 and a space modulation lightgeneration unit 16.

The light source unit 12 includes a green laser diode LD(G), a bluelaser diode LD(B) and a red laser diode LD(R) Each laser diode is fedfrom a power source apparatus 52 of the power source system 50 to emiteach color laser light.

Incidentally, the power source system 50 includes a power sourceapparatus 52, which outputs a voltage and a current for driving thelasers to the light source unit 12, and a regulator 54. The power sourcesystem 50 is constituted so as to be able to adjust the output level ofthe power source apparatus 52 by means of the regulator 54 (in theoutput adjustment, a current or the like output from the power sourceapparatus 52 to the light source unit 12 can be arbitrarily adjustedover a region of from zero to the maximum permitted value according to acommand from the entry detection and danger prevention control unit110).

The illumination light generation unit 14 is provided for accepting thelaser light of each of the colors R, G and B emitted from the lightsource unit 12 to generate parallel illumination lights. Theillumination light generation unit 14 includes a green illuminationoptical unit LG(G), a blue illumination optical unit LG (B) and a redillumination optical unit LG(R).

The space modulation light generation unit 16 includes opticalmodulation means. In the present embodiment, a one-dimensional opticalmodulator called as a grating light valve (GLV) is used. The element isconstituted by using a phase diffraction grating capable of electricalon-off control of light (the element is used for digital image display).

For each color light from the illumination light generation unit 14, aGLV (G) for green, a GLV (B) for blue and a GLV (R) for red areseverally provided. The space modulation light generation unit 16further includes a combiner “MX”. A drive signal for modulationaccording to an image signal (VIDEO) to be processed by the signalprocess unit 60 is severally supplied to each color GLV from a drivercircuit 64. The light from the illumination light generation unit 14 ismodulated according to the image signal VIDEO to be output.

The combiner “MX” is means for synthesizing the light from each colorGLV (image synthesis means). The output light of the combiner “MX” isemitted to the optical adjustment unit 20 at the subsequent stage.

The optical adjustment unit 20 includes an Offner relay optical system22 and a diffuser optical system 24. The optical adjustment unit adjustsimage light from the space modulation light generation unit 16.

The optical projection unit 30 located at the subsequent stage of theoptical adjustment unit 20 includes the projection lens 32 and a scanner34. The optical projection unit 30 constitutes light projection means ofan image on the screen. The screen 40 for projection is arranged infront of the optical projection unit 30. An image corresponding to theimage signal VIDEO is projected on the screen 40 by the scanner 34,which is equipped with deflection means such as a galvanometer mirror orthe like. Incidentally, in the present embodiment, the form in which thescanner 34 is arranged at the subsequent stage of the projection lens 32is shown. However, the optical projection unit 30 maybe implemented invarious configurations such as the form in which the positional relationbetween the both of the scanner 34 and the projection lens 32 isreversed (the form of performing expansion projection after scanning),and the like.

The signal process unit 60 includes an image signal process unit 62, thedriver circuit 64, an overall control unit 66 and a scanner control unit68.

The image signal VIDEO from image source equipment (such as a computer,a recording and reproducing apparatus, or the like), which is not shown,is input into the image signal process unit 62. A signal process forgenerating a signal for modulating illumination light (laser lights) bycontrolling each GLV of the space modulation light generation unit 16 ofthe driver circuit 64 is performed. Then, the driver circuit 64 receivesan output signal from the image signal process unit 62, and then a drivesignal to each color GLV to drive each element.

The scanner control unit 68 is provided for performing the rotationcontrol of the scanner 34, and is controlled by the overall control unit66. Incidentally, the overall control unit 66, for example, transmits acommand to the scanner control unit 68 in response to a signal from thedriver circuit 64, and controls the whole image signal process, andfurther performs projection control and the like.

FIG. 10 is a flowchart representation showing an example of theprocesses in the entry detection and danger prevention control unit 110.Process steps S1-S6 are as follows:

-   -   (S1) a start of the apparatus,    -   (S2) radiation of light of class 1, and a position adjustment,    -   (S3) a level adjustment of class 3R,    -   (S4) a passage confirmation test,    -   (S5) an end of the adjustment, and    -   (S6) a setting of a normal monitoring state.

Incidentally, (S1)-(S5) concern an initial adjustment. (S6) is set whenthe apparatus is started to be used after the initial adjustment.Moreover, both of (S2) and (S3) are steps pertaining to a radiationadjustment of a laser light. The laser light is made to be reduced tothe sufficiently safe intensity for the eye in case of the radiationlevel of the “class 1” at (S2). Moreover, the radiation level of the“class 3R” at (S3) is the intensity to be used in a normal operation ofa projector apparatus (see “JIS C 6802” as to laser safety regulations).

Next, FIG. 11 is used for describing S1-S6 mentioned above.Incidentally, the abscissa axis of FIG. 11 indicates time, and theordinate axis indicates the radiation level of a laser light toexemplify the details of the changes thereof in point of time. Themeanings of each of the time t1-t4 and periods of time T1 and T2 are asfollows:

-   -   “t1”=a point of time when the power supply switch of the        apparatus is turned on,    -   “t2”=a point of time when a rise from the class 1 to the class        3R is started,    -   “t3”=a point of time when the human body or an obstacle start to        enter the monitoring space,    -   “t4”=a point of time when a rise to the class 3R is started,    -   “T1”=a period of time of the operation of APR, and    -   “T2”=a period of time of the entry into the monitoring space by        the human body or the obstacle (T2>T1).

In FIG. 11, the “APR” (Auto Power Reduction) indicates a safetymechanism for decreasing the laser power level when the entry by thehuman body or the like is detected. “ON” indicates an operation state ofthe mechanism, and “OFF” indicates a release of the cutting off of thelaser light after the operation of the mechanism.

First, at the step S1, an operator operates a power supply switch 140(see FIG. 9) of the projector apparatus to turn on the switch 140 at thepoint of time t1, and a start of the projector apparatus is instructed.Accordingly, feeding power to each unit of the projector apparatus isperformed. Incidentally, in the state in which the image signal VIDEO isnot supplied to the image signal process unit 62, only lighting withoutany image is performed (incidentally, it should be noted that the lightfrom the projection lens 32 does not always correctly project theprojection area 42 in this state).

At the next step S2, the radiation level (power) of the laser lightrises to the class 1. That is, at the point of time t1, when a signalindicating that the power supply switch 140 is on is input into theentry detection and danger prevention control unit 110, power control tothe light source unit 12 is performed, and a laser light having thepower of the class 1 is radiated. Then, a position adjustment on thescreen is performed.

In the state immediately after the apparatus main body unit 1A of theprojector apparatus and the screen 40 have been set, the infrared raysradiated from the infrared ray radiation units 120A-120D toward themonitoring areas 46A-46D do not always correctly irradiate expectedpositions.

Accordingly, in addition to the adjustment of the directivity or theprojection distance of each of the infrared ray radiation units, thefocal length adjustment of the projection lens 32 and the like areperformed by means or automatically as the occasion demands. Forexample, the direction of the apparatus main body unit 1A, the focallength of the projection lens 32, or the like is adjusted in order thatthe light from the projection lens 32 may be radiated in a regioncorresponding to the projection area 42 on the screen 40. Then, afterthe position of the projection area 42 on the screen 40 has beensettled, the positions of both of the radiation region on the screenfrom each of the infrared ray radiation units 120A-120D and each of themonitoring areas 46A-46D are adjusted so as to be in respectivelycorresponding positional relations.

Incidentally, with regard to the adjustments of the projection distance,the display position, an image size and the like, the alignment of theinfrared ray radiation region and the monitoring areas, and the like,the image means 100 is used for imaging the projection light from theprojection lens 32 to the screen 40 and the projection light of thelight-emitting diodes constituting each of the infrared ray radiationunits as the reflection light of them. Then, the image means 100 inputsthe image signals to the entry detection and danger prevention controlunit 110. Accordingly, the entry detection and danger prevention controlunit 110 performs the signal process of the image signals to make itpossible to confirm the adjustments and the alignment on the imagedisplay (in case of the adjustment of the projection area 42 and thelike, the infrared ray transmission filter (a visible light cuttingfilter) provided on the image means 100 is removed).

Moreover, it is necessary to secure the sufficient safety of infraredemission power.

FIG. 12 is a graphical representation exemplifying a relation betweeninfrared LED power and a distance.

The maximum permissible exposure (MPE) of a cornea to direct eyeexposure regulated in “JIS C6802” is 0.733 mW/cm² in the case where awavelength λ is 880 nm and a radiation time t is 3×10⁻⁴ seconds (0.3 ms). The present embodiment is also designed to meet the standard. Forexample, when a screen size is 80 inches and a projection distance is2.35 m, the power of the infrared rays in the monitoring area 46 isabout 0.15 mW/cm², and the infrared ray radiation width in themonitoring area 46 is 5 cm. As another example, when the screen size is180 inches and the projection distance is 6.53 m, the power of theinfrared ray in the monitoring area 46 is about 0.054 mW/cm², and theinfrared ray radiation width in the monitoring area 46 is 5 cm.

FIGS. 13A-13C are views for illustrating adjustments and confirmationprocesses of positional relations between each of the projection areasirradiated by the infrared ray radiation units 120A-120D and themonitoring areas 46A-46D. The present embodiment exemplifies the casewhere, after finishing the position adjustment to the projection area 42projected from the projection lens 32, an imaging result of the imagemeans 100 stored in the memory of the entry detection and dangerprevention control unit 110 is displayed on a display device, which isnot shown, to confirm the radiation state from the infrared rayradiation units 120A-120D to the monitoring areas 46A-46D.

FIG. 13A shows the initial state immediately after the projection area42 has been set. Around the projection area 42, numerical values of thedistances of projection regions 46 a-46 d (indicated by broken lines) ofthe infrared ray radiation units 120A-120D in the state of being distantfrom the outer edge of the projection area 42 severally by a distanced1=30 cm, a distance d2=20 cm, a distance d3=20 cm, and a distance d4=40cm.

The image means 100 images the reflection of the light of the infraredray radiation units 120A-120D irradiated on the screen 40 through aninfrared transmission filter. For example, the monitoring area widthsare set to be 5 cm, and the width directions severally correspond to thedata for 6 pixels. The length of each of the areas 46A and 46C in thelonger direction of the shown monitoring area 46 corresponds to the datafor 200 pixels, and the lengths of the areas 46B and 46D correspond tothe data for 114 pixels. Then, each pixel data is expressed as, forexample, data having 256 gradations.

The entry detection and danger prevention control unit 110 performs thesignal process of the image data input from the image means 100. Theentry detection and danger prevention control unit 110 binarizes thepixel data related to the projection regions 46 a-46 d by the use of athreshold value of, for example, 50 to distinguish the pixel data of 50or more as a logical value “1” from the pixel data less than 50 as alogical value “0”. Accordingly, the entry detection and dangerprevention control unit 110 displays the part of the projection area 42and the projection regions 46 a-46 d on a display screen. At that time,the entry detection and danger prevention control unit 110 calculatesthe intervals between the projection area 42 and the projection parts 46a-46 d to display the calculated intervals as the distances d1-d4.

In the present embodiment, the W value is set to be 10 cm. Consequently,the tilt angles of the infrared ray radiation units 120A-120D areadjusted in order that all of the distances d1-d4 may be about 10 cm.

FIG. 13B shows that the distances d1 and d3 are adjusted in the state inwhich the light from the infrared ray radiation units 120A and 120C isprojected in the areas 46A and 46C distant from the upper and the lowerperipheries of the projection area 42 by 10 cm, respectively. Moreover,FIG. 13C shows that the distances d2 and d4 are adjusted in the state inwhich the light from the infrared ray radiation units 120B and 120D isprojected in the areas 46B and 46D distant from the left and the rightperipheries of the projection area 42 by 10 cm, respectively.

Incidentally, the vale of W=10 cm is an example. It is needless to saythat it is necessary to perform the position settings of the projectionregions of infrared light or infrared rays and monitoring areas suitablyaccording to the changes of the angle of view owing to zooming or thelike.

When the position adjustment has been performed manually orautomatically in the state of FIG. 13C and successively the confirmationthereof has been ended, the process advances to the next step S3 of theadjustment process of the laser power at the class 3R. Incidentally, inthis case, the infrared ray transmission filter is attached to the imagemeans 100.

By increasing the supply power from the power source apparatus 52 to thelight source unit 12, the laser power which has been at the class 1 atthe point of time t2 rises to the class 3R. Incidentally, it is neededto set the APR operate at the time t2 for making the function of thesafety mechanism effective.

The reflection light (infrared ray) of each of the monitoring areas46A-46D is received by the image means 100. The entry detection anddanger prevention control unit 110 acquires the detected level of thereflection light, which is imaged by the image means 100 from the pixeldata to compare the acquired level with the reference region forexamining whether the acquired level is within a permitted region ornot. For example, when each pixel data is set to be expressed at 256gradations, the data is binarized by comparing with the threshold value.The pixel is distinguished by setting that the data equal to thethreshold value or more corresponds to the logical value “1”, and thatthe pixel data less than the threshold value corresponds to the logicalvalue “0”. Accordingly, it is needed to confirm whether the monitoringareas 46A-46D are correctly irradiated by the infrared rays.

Incidentally, according to experiments, the detected levels of the imagesensor (the CCD type image sensor) to various reflection surfaces werethe values shown in the following table 1. It is preferable to determinethe threshold value according to the quality of the material used forthe screen 40. For example, when the quality of the material of thescreen 40 is white mat screen, white paper or the like, the setting ofthe threshold value to be about 55 would make it possible todiscriminate a Japanese skin, one of entry detection objects. TABLE 1REFLECTION SURFACE DETECTION LEVEL OF CCD SENSOR Black Almite 255 WhiteMat Screen 73 White Paper 79 Gray Cloth 64 Corrugated Fiberboard 60Japanese Skin 38 Glossy Black Cloth 28

At the next step S4, a passage confirmation test of an obstacle to thepassage regions (truncated pyramid-like detection regions) of theinfrared rays projected from the infrared ray radiation units 120A-120Dtoward each of the monitoring areas 46A-46D, respectively, is performed.That is, an operator performs the test by putting in and out theobstacle in the detection regions surrounded by the infrared rays toconfirm whether a reducing or a rise of a detected signal level isdetected or not on the basis of the image data pertaining to themonitoring areas 46A-46D image means 100.

At the time t3 of FIG. 11, a situation in which entry by an obstacleinto the monitoring space surrounded by the infrared rays has beenstarted is shown. When this is detected, the APR operates to reduce thelaser power abruptly. Then, the laser power becomes zero within theperiod of time T1 (<T2) conclusive. That is, the laser power is reducedto the level equal to the class 1 or less during the period of timeshorter than the entry period of time T2 necessary for the obstacle toenter the projection region of the laser light.

Various forms can be cited as the test method. For example, by puttingin and out an object such as a human finger, a glossy black scale or thelike into each of the monitoring areas from the outside of the detectionregion, the lowering and the like of the detected signal level ischecked.

The entry detection and danger prevention control unit 110 performs thecontrol for making an alarm sound (an output signal is transmitted to aalarm apparatus, which is not shown) when the obstacle enters thedetection region in the passage test. Accordingly, the operator canconfirm with his or her hearing sense that the detection of the obstaclehas been normally performed. Moreover, the entry detection and dangerprevention control unit 110 can also make a not shown display devicedisplay the part corresponding to the obstacle in red or the likedistinguishingly as the occasion demands (in the monitoring area inwhich no obstacle is detected, the detected image is displayed in, forexample, white) . Then, the entry detection and danger preventioncontrol unit 110 can also store the data at this time in the memory.

Such a test is performed to the monitoring areas 46A-46D (incidentally,when it is previously apparent that no necessity of supposition of theentry or the passage of an obstacle exists, the corresponding monitoringarea is naturally removed from the test objects).

Incidentally, because the projection from the projection lens 32 to theprojection area 42 is unnecessary during the period of the test, it ispreferable that the entry detection and danger prevention control unit110 drives the regulator 54 to reduce the electric power to be fed fromthe power source apparatus 52 to the light source unit 12 to a very lowlevel, or to stop the feeding from the power source apparatus 52 to thelight source unit 12.

When the passage test is completed, the process advances to the nextstep S5 for ending the series of adjustment operations mentioned above.Incidentally, the order, the number of the performance, and the like ofS2-S4 maybe suitably changed.

When the adjustments and the confirmations have ended, the operatoroperates operation input means (an operational switch or the like),which is not shown, to instruct the end of the adjustments and theconfirmations to the entry detection and danger prevention control unit110.

When the feeding from the power source apparatus 52 to the light sourceunit 12 is stopped or is made to be the state of very less electricpower supply during the passage test, no trouble is caused even if theperson enters the region connecting the projection lens 32 with theprojection area 42. Consequently, when the operator issues theinstruction of the adjustment end, the entry detection and dangerprevention control unit 110 can stop the feeding from the feederapparatus 130 to the infrared ray radiation means 120.

On the other hand, for sending out an alarm for a person to enter thedetection region, it is also possible that the entry detection anddanger prevention control unit 110 can make the alarm to be outputalways by continuing the feeding from the feeder apparatus 130 to theinfrared ray radiation means 120 as long as the power supply switch 140is in the on state independent of the feeding state from the powersource apparatus 52 to the light source unit 12.

At the last step S6, the entry detection and danger prevention controlunit 110 sets the apparatus in the normal monitoring state.

For example, when the image signal VIDEO is input into the image signalprocess unit 62 from not shown image source equipment to start theprojection operation of the projector apparatus, the driver circuit 64outputs a drive signal corresponding to the image signal VIDEO to thespace modulation light generation unit 16, and the overall control unit66 controls the scanner 34 by means of the scanner control unit 68.

The information indicating the start of the normal projection operationis transmitted from the overall control unit 66 to the entry detectionand danger prevention control unit 110, and the entry detection anddanger prevention control unit 110 always detects whether a person, anobstacle or the like enters the area corresponding to the detectionregion (hereinafter referred to as an “entry prohibition area”) or not.

The detection method is similar to the method described at the step S4.However, it is preferable to take the following means when the entrydetection and danger prevention control unit 110 detects a person or thelike in the entry prohibition area, for the protection of the person.

Reducing the electric power supplied from the power source apparatus 52to the light source unit 12 by controlling the regulator 54 so as toreduce the level of the radiation light traveling from the projectionlens 32 toward the screen 40 to the level at the degree of causing notroubles in the naked eyes of the person.

According to a situation, cutting off the electric power to be suppliedfrom the power source apparatus 52 to the light source unit 12.

As a result of the means, the radiation light traveling from theprojection lens 32 toward the screen 40 becomes dark or nothing.Moreover, at this time, the entry detection and danger preventioncontrol unit 110 can output an alarm sound, an alarm message or thelike.

The danger prevention process by the entry detection and dangerprevention control unit 110 differs according to the situation when aperson enters the entry prohibition area.

For example, when the W value of each of the monitoring areas 46A-46D isset to be 10 cm and an entry speed is 2 m/s (meters every second), theduration of entry by a line-shaped object is 0.05 sec. Moreover, whenthe entry speed is a half (1 m/s) of the former case, the duration ofentry by a line-shaped object is 0.10 sec. If a human being enters intothe monitoring areas, the width of the person is wider than the width ofthe line-shaped object. Consequently, the entry time becomes longer than0.05-0.1 sec. by several folds to ten-some folds.

Moreover, a person is moving along a surface formed by connecting eachof the infrared ray radiation units to each of the monitoring areas (aboundary of the entry prohibition area), the person who enters themonitoring areas is in the state of staying in the entry prohibitionarea. When the length of each of the monitoring areas in their longerdirections is supposed to be 2 m, and when entry speed is supposed to be2 m/s, the person is staying the entry prohibition area for about onesecond.

On the other hand, noises are inevitably mixed to the image data imagedby the image means 100. Then, there is the possibility that an erroneousjudgment in which a person has instantaneously and partially entered theentry prohibition area is made (it is unnecessary to perform ahypersensitive judgment process in such a case).

Accordingly, it is preferable to perform a phased prevention processaccording to a multiplication result of an entry continuing time and thesize of an entry area.

Hereupon, the “entry continuing time” means a time during which an entrystate of the entry prohibition area is continuing. Moreover, the “sizeof an entry area” means the area of a part of the reflection light levelof each of the monitoring area 46A-46D detected by the image means 100which part deviates from a prescribed reference region (for example, thearea corresponds to the number of pixels having the data equal to thethreshold value or less) in the case where the part deviates from theregion.

The following table 2 exemplifies “entry state indication values”, whichis defined by a product of a continuing entry time and the size of anentry area (the area of the entry part or the like), and the contents ofprocesses performed by the entry detection and danger prevention controlunit 110 according to the products. TABLE 2 PROCESS CONTENTS OF ENTRYENTRY STATE DETECTION AND DANGER INDICATION VALUE PREVENTION CONTROLUNIT First Judgment Level or Less Nothing is Performed Second JudgmentLevel or Less Reducing the Power of The Light Source Unit 12 to 75% andOutputting a Slight Alarm Sound Third Judgment Level or Less Reducingthe Power of The Light Source Unit 12 to 50% and Outputting a StrongAlarm Sound Fourth Judgment Level or Less Stopping the Feeding to theLight Source Unit 12

In the present embodiment, four steps of processes according to theentry state indication values (reduces of the power of the light sourceunit and a stop of feeding) are performed. The entry detection anddanger prevention control unit 110 changes the electric power level ofthe power source apparatus 52 through the regulator 54 to adjust theoutput of the light source unit 12 for preventing bad influences to theeyes of the person who enters the entry prohibition area. Incidentally,the processes of the entry detection and danger prevention control unit110 according to the entry situations is not limited to the embodimentmentioned above. Various process methods can be performed. For example,a method of judging only by entry continuing times, a method of judgingonly by the size of an entry area (a planar dimension of the entry), amethod of judging by considering further different factors, and the likecan be cited.

When a person enters the entry prohibition area, it is possible toprevent any harm to the human body by the process described above. Inparticular, even when an infant or the like who cannot understand thesituation enters the entry prohibition area, a sufficient safety measurecan be taken.

Next, variation forms of the configuration will be described.

It is preferable to automate the adjustment of the inclination operationangle (the tilt angle) of each of the infrared ray radiation units120A-120D constituting the infrared ray radiation means 120. Byproviding a drive source such as a motor or the like and a tiltmechanism to each of the infrared ray radiation units, radiationdirection control can be performed through the attitude control by them.

Moreover, in the embodiment mentioned above, the example of advancing tothe normal monitoring process after the end of the adjustments at thestep S5 shown in FIG. 10 is described. However, when a projectorapparatus to which the adjustment operations have already ended is used,it is also possible to start from the normal monitoring state at thestep S6 immediately after the power supply switch 140 has been turnedon. In this case, for example, a flag (an adjustment end flag) forindicating the completion of the adjustment operation at the step S5 maybe prepared, and the flag may be set to a prescribed value (for example,“1”) to be stored in the memory in the entry detection and dangerprevention control unit 110.

In the normal monitoring state at the step S6, infrared rays arecontinuously radiated from each of the infrared ray radiation units120A-120D to each of the monitoring areas 46A-46D of the screen 40.However, the present invention is not limited to the embodiment. Theinfrared ray radiation may be performed at a time interval during whichit is possible to detect a person of the entry prohibition area (forexample, it is possible to perform the infrared ray radiation to themonitoring area 46 at several millisecond interval intermittently).

Moreover, in the embodiment mentioned above, the case where infraredrays are radiated from the infrared ray radiation means 120 to all ofthe monitoring areas 46A-46D is described. However, for example, whenthe position of the area 46A is high and there is no possibility of theentry into the area 46A in view of the region of the statures ofordinary persons, it is not necessary to dare to perform the infraredray radiation of the area.

In the above descriptions, the system in which the monitoring area 46located on the outside of the projection area 42 on the screen isprovided to monitor the entry into the entry prohibition area issupposed. However, it is possible to reinforce the monitoring system bysetting another monitoring area on the outside of the monitoring area tobe the multi-tiering (double-tiering, triple-tiering or the like) of themonitoring space. In the following, such an embodiment will bedescribed.

FIG. 14 is a block diagram showing a configuration example of theprojection system. The basic components are similar to those shown inFIG. 9 (accordingly, the functionally same components are designated bythe reference letters which have been already attached, and duplicatingdescriptions are evaded), and only different points are shown in thefollowing in the state of being itemized.

-   -   The monitoring area is made to be double-tiered. A first alarm        process unit 70 takes charge of the inside area (a first        monitoring space or a first monitoring zone), and a second alarm        process unit 80 takes charge of the outside area (a second        monitoring space or a second monitoring zone) Entry to each of        the monitoring spaces is severally detected, and an alarm        process is performed according to the state or the situation of        the entry.    -   The first alarm process unit 70 includes first detection means        72 and first alarm means 74. When entry by the human body or the        like is detected by the first detection means 72, the first        alarm means 74 outputs an alarm, and changes the intensity of        the laser light (reducing or zero).    -   The second alarm process unit 80 includes second detection means        82 and second alarm means 84. When entry by the human body or        the like is detected by the second detection means 82, the        second alarm means 84 outputs an alarm.

FIGS. 15A and 15B are schematic views showing a positional relationbetween the main body unit 1B of the projector apparatus and the screen40. FIG. 15A is a perspective view showing a state of projection light,and FIG. 15B is a sectional view in case of being viewed from thedirection (a lateral direction) perpendicular to the projectiondirection.

An image projected from the optical projection unit 30 of the main bodyunit 1B to the screen 40 is scanned by the scanner 34 of the opticalprojection unit 30 to be projected in the projection area 42 of thescreen.

A passage area 42S of the light (image light) to be projected from theoptical projection unit 30 to the projection area 42 is called as an“image light passing space area”.

Moreover, it is supposed that the first monitoring space (or zone) iscomposed of the following areas.

-   -   A “first monitoring area”=a monitoring area located on the outer        periphery of the projection area 42 (similar to the monitoring        area 46 mentioned above. The width of the first monitoring area        is exaggeratingly shown in the drawing).    -   A “first space monitoring area”=a space area located on the        outside (outer periphery) of the image light passing space area        42S (a space area 46S located around the image light output from        the optical projection unit 30).

Similarly, the second monitoring space (or zone) is assumed to becomposed of the following areas.

-   -   A “second monitoring area”=an external area 90 including the        outer periphery of the first monitoring area 46 or the first        monitoring area 46 (an area shown by a broken line in FIG. 15A).    -   A “second space monitoring area”=a space area 90S including the        outer periphery of the first space monitoring area 46S or the        first space monitoring area 46S (see FIG. 15B).

In the first alarm process unit 70 (see FIG. 14), the first detectionmeans 72 detects entry into the first space monitoring area 46S by thehuman body or an object, or detects the continuous existence of them.Then, the first alarm means 74 outputs an alarm on the basis ofdetection information from the first detection means 72, and controlsthe electric power supply to the light source unit 12.

Moreover, in the second alarm process unit 80, the second detectionmeans 82 detects entry into the second space monitoring area 90S by thehuman body or an object, or detects the continuous existence of them.Then, the second alarm means 84 outputs an alarm on the basis ofdetection information from the second detection means 82.

FIG. 16 is a flowchart representation showing an example of an alarmprocess. The process is performed in accordance with the followingsteps:

-   -   (S11) a normal projection operation,    -   (S12) entry detection by the second detection means,    -   (S13) an alarm process by the second alarm means,    -   (S14) entry detection by the first detection means, and    -   (S15) an alarm process by the first alarm means.

First, at the step S11, the light source unit 12 is driven by theregulated voltage from the power source apparatus 52 in FIG. 14, and theimage light modulated by the space modulation light generation unit 16according to the image signal VIDEO is projected from the opticalprojection unit 30 into the projection area 42 on the screen 40.

Then, the alarm operation advances to the step S12, and the seconddetection means 82 detects whether the human body or the like enters thesecond space monitoring area 90S or not. That is, when entry or theexistence of the human body or the like is detected, the alarm operationadvances to the step S13, and the second alarm means 84 performs analarm process. As the alarm process, an audio message of the content,for example, “Danger. Please keep away from the projection area.” isoutput (because a viewer can hear the message even in the state in whichhe or she does not gaze at the projection area 42, the viewer canpreviously perceive a danger). Accordingly, the person is urged to anevasive action. Incidentally, in addition to the audio message, orindependent of the audio message, an image display may be performed inthe projection area 42 by the following process. That is, a second alarmsignal is outputted from the second alarm means 84 to the overallcontrol unit 66. Then, the overall control unit 66 makes the imagesignal process unit 62 superpose an alarm message signal or an alarmpattern signal on the image signal VIDEO to output the superposed imagesignal VIDEO to the driver circuit 64. Thus, the image display isperformed through the space modulation light generation unit 16(Accordingly, the viewer can previously perceive the danger by the alarmdisplay on the projection area 42 and the audio message).

When the entry or the like is continuing despite these alarms, at thenext step S14, the first detection means 72 detects the entry into thefirst space monitoring area 46S. That is, when the entry by the humanbody or the like or the existence of the human body or the like in thearea 46S is detected, the alarm operation advances to the step S15 toperform a first alarm process by the first alarm means 74. For example,the first alarm means 74 cuts off an output voltage of the power sourceapparatus 52 by the regulator 54 in order to make the laser light fromthe light source unit 12 be not emitted. Consequently, the eyes of theviewer are protected. It is preferable to output an audio message of thecontent such as “Danger. The apparatus is stopped.” (the reason of thestopping of the projector apparatus can be realized by the viewer).

Incidentally, the first alarm means 74 may reduce the output of thepower source apparatus 52 by means of the regulator 54 to reduce theintensity of the laser light to a safe level, and thereby the eyes ofthe viewer may be protected. At that time, it is preferable to makearrangement for the viewer to understand the reason of the reducing ofthe projection light by outputting an audio message of content such as“Dangerous for your eyes. The laser light is darkened.”

Moreover, when the first alarm means 74 operates, the first alarm means74 outputs a first alarm signal to the overall control unit 66, and theoverall control unit 66 requests an external apparatus, which outputsthe image signal VIDEO to stop the outputting of the image signal VIDEO,as the occasion demands. Thus, the projection of the projector apparatuscan be stopped.

A restart of the projector apparatus after the first alarm means 74 hasoperated can be performed by resetting the regulator 54 by an operationof an operator. With regard to the resuming of output of the imagesignal VIDEO from the external apparatus such as computer equipment orthe like, the overall control unit 66 request an image signal to theexternal apparatus when the projector apparatus is restarted by theoperator.

According to the above embodiment, when entry into the second spacemonitoring area 90S is detected, and further, when entry into the firstspace monitoring area 46S is detected, the laser light is cut off or thelight intensity thereof is reduced. Accordingly, it is possible to takethe safety measure without lowering the rate of operation of theprojector apparatus in comparison with that of one-step entry detection.Then, before the entry into the first space monitoring area 46S, theentry into the second space monitoring area 90S by the human body can bedetected, and an advance alarm can be performed. Consequently, it ispossible to prevent the erroneous entering of the human body into theentry prohibition area beforehand.

It is preferable that the first alarm means 74 performs the alarmprocess when the first detection means 72 detects entry into the firstspace monitoring area 46S within a prescribed time from the point oftime when the second alarm means 84 has operated. Accordingly, theerroneous detection or malfunctions of the first detection means 72, orthe influences of noise components at the time of the detection of thefirst space monitoring area 46S are reduced, and a defect of thereducing of the availability of the projector apparatus owing tofrequency operation of the first alarm means 74 can be prevented.

The following forms can be cited as embodiments of the second detectionmeans 82 of the second alarm process unit 80:

-   -   (I) a form using a pyroelectric sensor (which is used for        detecting entry by the human body in a guard apparatus or the        like) for detecting radiation energy emitted by the human body,        and    -   (II) a form using a heat detection sensor to be used for a        thermography apparatus and the like.

With regard to the form (I), for example, the following forms can becited:

-   -   (I-1) a form using a pyroelectric sensor (see FIG. 17), and    -   (I-2) a form combining a plurality of pyroelectric sensors (see        FIG. 18).

First, in the form (I-1), for example, as shown in FIG. 17, as a settingmethod of the pyroelectric sensor, a pyroelectric sensor having adirective characteristic to an area surrounding almost the whole of thesecond monitoring area 90 including the screen 40 (the area is shown bya thick line circular frame) can be provided in the neighborhood of theoptical projection unit 30. Incidentally, for preventing the frequentoperation of the second alarm means 84 caused by malfunctions, noisesand the like, the second alarm means 84 may be operated when thepyroelectric sensor continue to detect the human body or the like for aprescribed time or longer (for example, a threshold value for judgingthe duration is set to about two seconds).

As the first detection means 72, as described above, an image sensor(CCD sensor or the like) can be used. The form in which the image sensoris commonly used by the second detection means 82 is also possible, ofcourse. In that case, an entry state of the first space monitoring area46S can be also detected by means of a pyroelectric sensor (thepyroelectric sensor functions as the first and the second detectionmeans). Moreover, the detection of entry into the image light passingspace area 42S by the human body can be also detected by means of thepyroelectric sensor.

In (I-2) mentioned above, for example, a plurality of pyroelectricsensors having a relatively narrow directivity can be used. A pluralityof circular frames shown in FIG. 18 indicates a detection area by eachpyroelectric sensor. At the lower part of the drawing, the directivitydistributions of the pyroelectric sensors are schematically shown. Inthe present variation, seven pyroelectric sensors are used. The sevenpyroelectric sensors are arranged in the neighborhood of the opticalprojection unit 30 so as to be directed to the lower part, the rightside part and the left side part of the second space monitoring area 90Sseverally. Incidentally, because it is impossible that a personapproaches to the upper part of the second space monitoring area 90S, itis supposed that the necessity for providing pyroelectric sensorsdirected to the part does not exist.

With regard to the pyroelectric sensors taking charge of the lower partof the second space monitoring area 90S, an example of the intensitydistribution of the directivity is shown as three waveforms. However,because not so much strict conditions are required as the directivity,the directivity may be set to be directed to the outside of the firstspace monitoring area 46S or a region including the area 46S.

In this case also, for evading the frequent operation of the secondalarm means 84 owing to malfunctions, noises and the like, the systemmay be constituted so as to operate the second alarm means 84 when eachpyroelectric sensor continues to detect the human body for a prescribedtime or longer.

Moreover, when two pyroelectric sensors are combined to be used, forexample, when two pyroelectric sensors are parallelly arranged to becoupled and a difference between detected signals by the coupledpyroelectric sensors is calculated, the moving direction of the humanbody can be detected on the basis of the sign (±) of the difference. Thepair of pyroelectric sensors are used as a differential pyroelectricsensor by being arranged to be directed to the lower part, the rightside part and the left side part of the second space monitoring area90S, the human body invading the second space monitoring area 90S can bedetected.

Next, the form (II) will be described. By means of a heat detectionsensor, the temperature of the human body (a body temperature) isdetected to enable the performance of a display, control and the likeaccording to the temperature. For example, when a temperature detectedby the heat detection sensor is within the region of a person's bodytemperature (34-40 degrees), it is judged that the human body exists inthe second space monitoring area 90S, and then the second alarm means 84operates. Incidentally, the detection area of the heat detection sensorcan be regulated similarly in the case of the pyroelectric sensor.Moreover, it is also possible to use the heat sensor commonly with thefirst detection means 72. In this case, a heat detection sensor isprovided as the first detection means 72 in the neighborhood of theoptical projection unit 30 to detect the human body existing in thefirst space monitoring area 46S, and further the heat detection sensorcan be used to detect the human body existing in the image light passingspace area 42S.

Besides, by providing a plurality of heat detection sensors in theneighborhood of the optical projection unit 30, the existence of thehuman body around the second space monitoring area 90S can be detected.

Next, the following configuration forms of the first detection means 72will be described:

-   -   (i) a form using ultrasonic sensors (see FIG. 19), and    -   (ii) a form using an optical sensor (see FIG. 20).

First, in the form (i), as shown in a circular frame in FIG. 19, aplurality of ultrasonic sensors (for example, about four sensors) whichincludes the first monitoring area 46 and the first space monitoringarea 46S as detection areas, and which does not include the secondmonitoring area 90 and the second space monitoring area 90S as detectionareas is used (each ultrasonic sensor is provided in the neighborhood ofthe optical projection unit 30). The ultrasonic sensors are equippedwith transmission and reception units. By applying a voltage topiezoelectric elements, ultrasonic waves are generated. By receivingultrasonic waves, electric signals according to the amplitudes of thereceived ultrasonic waves are outputted. In the state of thenonexistence of entry by the human body or the like, nothing interruptsthe ultrasonic waves between the optical projection unit 30 and thescreen 40. Then, in this case, ultrasonic waves are outputted from theultrasonic sensors, and advance to the screen 40 including the firstmonitoring area 46 of the screen 40. Reflection waves reflected on thescreen 40 are received by the ultrasonic sensors. When an object or thehuman body interrupting the ultrasonic waves exists between theultrasonic sensors and the first monitoring area 46 or the first spacemonitoring area 46S, their existence is judged by the reducing of thelevels of the reflection waves or the nonexistence of the detection ofthe reflection wave.

In the form (ii), for example, as shown in a black thick linerectangular frame in FIG. 20, a photo acceptance unit group such as aplurality of optical sensors, a line-shaped sensor (a linear CCD) or thelike is arranged along the first monitoring area 46 of the screen 40. Onthe other hand, a light-emitting device group (LED or the like)outputting light, infrared rays or the like, which has a sufficientlylower level than the level of the radiation light from the light sourceunit 12 from the periphery of the optical projection unit 30 toward thefirst monitoring area 46 is provided on the front surface of theprojector apparatus main body unit. Accordingly, an object or the humanbody interrupting the optical path formed between the light-emittingdevice group and the photo acceptance unit group can be detected.Alternatively, a configuration form in which a light-emitting devicegroup of infrared rays is arranged in the first monitoring area 46 andthe light emitted by the light-emitting device group is detected byoptical sensors of the projector apparatus main body unit may be cited.

It is needless to say that various embodiments such as ones usingpyroelectric sensors, heat detection sensors or the like, and one usingthe optical sensors commonly with the second detection means 82 can beadopted.

Incidentally, in the above descriptions, the example in which the firstmonitoring area 46 is regulated on the outer periphery of the projectionarea 42 on the screen 40 is exemplified. However, the first monitoringarea 46 may be unnecessary to be within the inside of the screen 40 aslong as the first monitoring area 46 is located on the outside of theprojection area 42. Moreover, the example in which the second monitoringarea 90 is located on the outside of the screen 40 is described.However, it is also possible to locate the second monitoring area 90 inthe inside of the screen 40 together with the first monitoring area 46.

By the configuration described above, for example, the followingadvantages can be obtained.

-   -   Because a laser light can be cut off or darkened while the human        body or an obstacle enters the projection area of the laser        light, safety is high.    -   The detection wave (infrared light or infrared rays) to be used        for the entry detection of the human body or an obstacle is        invisible to a viewer. Consequently, there is no defect in which        the detection wave influences a projection image on the screen        to deteriorate the image quality thereof. Moreover, the danger        owing to the influence of the detection wave itself to the human        body does not exist.

As apparent from the above descriptions, according to the presentinvention, it is possible to secure the safety to the human body, and torealize the entry detection into the monitoring space simply.

According to the present invention, it is suitable for theminiaturization of an apparatus.

According to the present invention, the precision of detection issufficiently secured, and no influences to a projected image exist.

According to the present invention, image detection can be surelyperformed, the width of the monitoring area can be set to the minimumnecessary in comparison with the method in which the whole region of theperiphery of the screen is monitored, and the detection process issimple and fast.

According to the present invention, a radiation light is regulated tosuppress the influences thereof to the human body, and thereby asufficient safety measure can be taken.

According to the present invention, in the application to an imageprojection apparatus equipped with optical modulation means, theimprovement of safety and reliability is effectively performed.

According to the present invention, by the cutting off of emission lightor the stopping of modulation of emission light, a rapid process can berealized.

According to the present invention, by controlling the supply power tothe light source, the light intensity can be surely regulated.

According to the present invention, detailed light output level controlaccording to the degree of an entry state can be performed. Moreover,erroneous detection prevention or the like is effectively performed.

According to the present invention, an entry detection process is easy,and does not need any complicated image process and the like.

According to the present invention, because the intensity of a radiationlight is suppressed until the safety is confirmed, high safety can besecured.

According to the present invention, by a multi-tiered monitoring system,the safety measure is effectively reinforced.

1. An image projection apparatus comprising a light source andprojection unit for performing an image display by projection to aprojection area on a screen, and a safety mechanism against entry into apassage area of a radiation light from said projection unit toward saidprojection area, characterized by comprising: a detection wave sourceprovided on an opposed plane of an apparatus main body unit to saidscreen or on said screen; and reflection wave detection means fordetecting a reflection wave reflected in a monitoring area, which islocated on an outside of said projection area at a distance, after adetection wave is emitted from said detection wave source toward saidmonitoring area, wherein entry into a monitoring space surrounded bysaid detection wave is detected on a basis of a result of a comparisonof a detected level by said reflection wave detection means with athreshold value or a reference region.
 2. The image projection apparatusaccording to claim 1, characterized in that said detection wave sourceor said reflection wave detection means is arranged around saidprojection unit provided on said opposed plane to said screen.
 3. Theimage projection apparatus according to claim 1, characterized in thatsaid detection wave is an infrared light or an infrared ray.
 4. Theimage projection apparatus according to claim 3, characterized in thatsaid reflection wave detection means is composed of an image sensor, andsaid monitoring area is monitored on a basis of detected image data bysaid image sensor, and a width of said monitoring area is made to benarrower than an area projected on said screen by said detection wavesource.
 5. The image projection apparatus according to claim 1,characterized in that if entry into said monitoring space is detected,an radiation light from said light source to said projection area is cutoff or intensity of said radiation light is reduced.
 6. The imageprojection apparatus according to claim 1, characterized by comprising:optical modulation means for modulating emission light from said lightsource according to an image signal; light projection means forprojecting said light modulated by said optical modulation means to saidprojection area on said screen; and entry detection means for detectingentry into said monitoring space, wherein, if said entry into saidmonitoring space is detected by said entry detection means, saidradiation light from said light source to said projection area is cutoff or intensity of said radiation light is reduced according to anentry state.
 7. The image projection apparatus according to claim 6,characterized in that if said entry into said monitoring space isdetected by said entry detection means, light emitted from said lightsource is cut off.
 8. The image projection apparatus according to claim6, characterized in that if said entry into said monitoring space isdetected by said entry detection means, electric power to be supplied tosaid light source is reduced or set to be zero.
 9. The image projectionapparatus according to claim 6, characterized in that if said entry intosaid monitoring space is detected by said entry detection means, a driveof said optical modulation means is stopped.
 10. The image projectionapparatus according to claim 8, wherein said electric power to besupplied to said light source is controlled according to a duration ofsaid entry into said monitoring space or the area of a part entered. 11.The image projection apparatus according to claim 1, characterized inthat said reflection wave detection means measures intensity of saidreflection wave from said screen on a basis of respective pixel data ofsaid monitoring area, and compares intensity of detection wave reflectedat a time of entry into said monitoring space with reflection intensityfrom said monitoring area in case of said entry does not exist, and saidentry is detected if both of said intensity differ from each other. 12.The image projection apparatus according to claim 1, characterized inthat an image is projected with said intensity of said radiation lightreduced to a level safe for the human body until no detection of anyentry into said monitoring space is confirmed, and after saidconfirmation, said intensity of said radiation light rises to a presetlevel.
 13. The image projection apparatus according to claim 1,characterized in that said reflection wave detection means comprises:first detection means for detecting said entry into said monitoringspace; second detection means for detecting entry into a monitoringspace including an outside area of said monitoring space; first alarmmeans for performing an alarm process if said entry is detected by saidfirst detection means; and second alarm means for performing an alarmprocess if said entry is detected by said second detection means. 14.The image projection apparatus according to claim 13, characterized inthat if said first detection means detects said entry, said radiationlight from said light source toward said projection area is cut off orsaid intensity of said radiation light is reduced to a level which isnot dangerous for human body.
 15. An image projection methodcharacterized by: setting a monitoring area, which is located on anoutside of a projection area on a screen, for said screen located at adistance from an image projection apparatus; emitting a detection wavefrom a detection wave source provided on a front plane of said imageprojection apparatus toward said monitoring area; detecting entry into amonitoring space surrounded by said detection wave by detecting areflection wave from said monitoring area; and cutting off lightradiated toward said projection area or reducing intensity of said lightaccording to an entry state.
 16. The image projection method accordingto claim 15, characterized in that infrared light or infrared rays areused as said detection wave.
 17. The image projection method accordingto claim 16, characterized by: monitoring said monitoring area having awidth narrower than that of said area projected on said screen by saiddetection wave source on a basis of image data detected by an imagesensor.
 18. The image projection method according to claim 15,characterized by: setting a first monitoring space including saidmonitoring area and a passage area through which a detection wave from afront surface of said image projection apparatus to said monitoringarea, and a second monitoring space provided on an further outside ofsaid monitoring area; and detecting entry into each of said monitoringspaces severally to perform an alarm process according to an entrystate.